current I(t) leads voltage V(t) by 180o
current I(t), lags voltage V(t) by 90o
over a full cycle the capacitor C does not consume any energy from the voltage source
current I(t) is in phase with voltage V(t)
Power, P = VrmsIrmscosφ ⇒ cosφ = 0 (as φ = 90° between Irms and Vrms across a capacitor)
Therefore, power consumed = 0 in one complete cycle across a capacitor.